2.0 Analysis 2.1 Separation During the Dumping Procedure Although crew members from the tug were required to board the SEA-LINK RIGGER to handle the ballasting during the cargo discharging operation, the barge was classed as unmanned, and as such, was not required by regulation to have a stability book for the guidance of those operating the equipment. Consequently, a precise analysis of the stability characteristics of the loaded barge at the time of the capsizing is not possible, and stability calculations cannot be made to determine accurately the cause of the capsizing. However, separation of the barge from the log cargo at the time of the dumping operation is at its most forceful during the fast dump of a barge with a high, relatively unstable load and little ballast water on board. The SEA-LINK RIGGER was carrying a low, stable load and had taken additional ballast water in the double-bottoms in an attempt to bring about the dumping of the cargo. When the load of logs dumped, the barge did not separate from the cargo and was rolled beyond its beam ends and capsized. 2.2 Tank Flooding and Dewatering System (Pumps and Blowers) The valves for flooding and pumping out the tipping and double-bottom tanks were located in the two pump-rooms. They were manually operated in the pump-rooms, with neither extended spindles nor remote actuation to permit their operation from the deck of the barge, or by radio from the wheel-house of the tug. This required the crew to go below decks into the pump-rooms to operate the tank and sea chest valves before the tipping and double-bottom tanks could be flooded. In this particular instance, the crew had to go into the pump-rooms to operate the double-bottom tank valves while the barge was already at its normal dump angle. This resulted in the mate becoming trapped in the after pump-room when the load dumped and the barge capsized. The air vents for the tipping and double-bottom tanks did not have automatic shut-off valves which would have eliminated the need for the crew to manually close the valves prior to blowing out the tanks. 3.0 Conclusions 3.1 Findings The SEA-LINK RIGGER was loaded with logs having a high specific gravity. The low, stable load did not dump when the barge was heeled with the tipping tanksfilled. The barge's double-bottom tanks were also filled to increase the heel. When the logs did not initially dump with the double-bottoms filled, preparations were begun to discharge by crane. The system for flooding the tipping and double-bottom tanks required the crew to go below decks on the barge to operate valves. The barge did not separate from the load when the logs dumped and it was rolled beyond its beam ends and capsized. The mate had to enter the after pump-room, inside the barge's hull, to start the pumping out operation, and he became trapped when the barge capsized. The air vent pipe valves were not automatic sealing types and required manual operation prior to blowing out the tanks. There were no as fitted diagrams of the piping/pumping systems on the barge or tug for use by the tug's crew during unloading or ballasting. The instructions contained in the company Operations Manual are not specific to the loading/discharging operations of the SEA-LINK RIGGER. 3.2 Causes The SEA-LINK RIGGER capsized when, in a ballasted condition, it did not separate from a slow-dumping load of high-specific-gravity logs and the dynamics of the dumping operation rolled the barge past its beam ends. During the capsizing, a crew member from the tug ARCTICHOOPER became trapped in a pump-room of the overturned barge because personnel were required to proceed below decks to control ballasting operations. The Board has no marine safety recommendation to issue at this time.4.0 Safety Action The Board has no marine safety recommendation to issue at this time.